Detecting Traces of Light-Quark Yukawa Couplings to the Higgs Boson in Fragmentation Products

Abstract: We point out that Yukawa interactions of light quarks with the Higgs boson are imprinted as unique azimuthal modulations in the density of fragmentation hadrons relative to the Higgs $p_T$. We introduce Yukawa Fragmentation Asymmetries (YFAs), interference observables that are linearly proportional to real (Standard Model) or CP-odd Yukawa couplings, respectively. The chiral suppression is lifted nonperturbatively by chiral-odd multi-hadron fragmentation functions. As a case study, we consider $VH$ production with a tagged target fragmentation hadron at the HL-LHC. We estimate that the YFAs from this single example process are already competitive with current projected HL-LHC sensitivities for second-generation couplings, and outperform them by a factor of 2-3 for first-generation couplings. Our results point to deep synergies between precision studies of confinement and the in-depth exploration of the Higgs sector.